Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $10.95   5.296%   $11.5299   $11.53   $11.55   $11.50  
  Purchase #2 $247.45   6.673%   $263.9623   $263.96   $263.95   $264.00  
  Purchase #3 $211.74   3.850%   $219.892   $219.89   $219.90   $219.90  
  Purchase #4 $210.54   11.472%   $234.6931   $234.69   $234.70   $234.70  
  Purchase #5 $49.85   13.768%   $56.7133   $56.71   $56.70   $56.70  
  Purchase #6 $157.46   10.107%   $173.3745   $173.37   $173.35   $173.40  
  Purchase #7 $214.47   13.723%   $243.9017   $243.90   $243.90   $243.90  
  7 purchase totals = $1,102.46       $1,204.0668   $1,204.05   $1,204.05   $1,204.10